New Delhi: Two Air India crew members have been caught allegedly smuggling three kilograms of gold worth over Rs 78.1 lakh on a domestic flight, Customs Department has told the national carrier.

The sources said Customs has also warned that Pilots and cabin crew of national carrier Air India are posing "significant security risk" by directly exiting the Mumbai Airport without clearing Customs.

In a communication sent yesterday, Assistant Commissioner of Air Intelligence Unit of Customs department has conveyed to Air India that it has come to the notice of the department that Pilots and crew of the national carrier do not go through the Customs.

"This poses a significant security risk," the officer said in a warning. Sources said the Customs has also cited instances of two crew members of Air India-- Nihal Prajapati and Sidhesh Patil, who were caught for allegedly smuggling gold worth over 78.1 lakh on a domestic flight from Mumbai.

The Customs department had directed the Air India to ensure that all their crew members and Pilots conform toprocedure at the airport with a warning that deviations would be "viewed seriously", the sources said.

The SMS sent to Air India spokesperson seeking his reaction on the issue remained unanswered. Earlier, also Directorate of Revenue Intelligence had warned about the alleged smuggling by Air India crew members.

In a letter written by the then Director General of DRI Najeeb Shah, Air India was asked to sanitise its staff,especially those involved in ground-handling duties, official sources said.

The DRI has also cited some past incidents of gold smuggling by Air India staffers in its missive, they said.

The DRI is understood to have sought a detailed enquiry report regarding those staffers held for illegally bringing gold into the country.

In 2013, an Air India air hostess and her friend were arrested by DRI from Calicut International Airport forallegedly trying to smuggle into the country 6 kg of gold, officials said.

In October that year, 32 kgs of gold biscuits, worth Rs. 15 crore in the international market, were recovered from the lavatory of an Air India flight when it reached Chennai from Dubai. Four persons were later arrested in the case, they said.